The present invention relates generally to systems for electronically controlling and managing the operation of drivetrain components including internal combustion engines and change gear transmissions, and more specifically to such systems for controlling such drivetrain components during gear shifting operations.
Electronic control systems for managing the operation of internal combustion engines are well known and widely used in the automotive and tractor truck industries. Such systems are typically operable to control engine fueling as well as many other engine and/or vehicle operating conditions.
Designers of electronic engine control systems have heretofore devised numerous techniques for controlling engine fueling during various engine operating conditions, and one such technique is illustrated in FIG. 1. Referring to FIG. 1, a prior art technique for controlling engine fueling to thereby limit engine speed during manual gear shifting operations is illustrated, wherein such a technique is commonly referred to as progressive shift control. FIG. 1 shows a graph of engine RPM vs. vehicle speed, wherein a linear engine speed limit 10 is typically established by specifying a first engine speed limit RPM1 at a first vehicle speed VS1 and a second engine speed limit RPM2 at a second vehicle speed VS2. The engine speed limit 10 linearly increases from RPM1 to RPM2 between VS1 and VS2 and is held constant at RPM2 beyond VS2, wherein RPM2 is typically less than rated engine speed 12. Rated engine speed, also known as governed engine speed, is defined for purposes of the present invention as the engine speed at which the engine produces an advertised engine output horsepower or torque value.
The purpose of progressive shift control is to gradually increase available engine speed (and thus more engine power) as vehicle speed increases between VS1 and VS2, wherein typical values for VS1 and VS2 are 0.0 and 40 mph respectively. This engine speed limiting scheme accordingly encourages the vehicle operator to manually shift gears at lower engine speeds than may otherwise occur, particularly in the lower transmission gears, thereby resulting in fuel savings associated with more efficient engine operation. This feature is illustrated by gear shifting pattern 14 wherein three gear shifts are shown, each occurring at progressively increasing engine speed values.
While the progressive shift control feature 14 illustrated in FIG. 1 achieves the goal of encouraging vehicle operators to shift at lower engine speeds, it has certain drawbacks associated therewith. For example, under high engine load operating conditions, such as when traversing a grade and/or when hauling a heavily loaded trailer, providing a hard limit 10 on available engine speed can hinder the drivability of the vehicle. One example of such hindered drivability is shown by shifting pattern 16 of FIG. 1, which illustrates the effect on the shifting pattern 14 of a steep grade encountered by the same vehicle. Under such operating conditions, the limit 10 on engine speed causes the vehicle operator to shift sooner than would otherwise be preferred and the effect of the steep grade causes additional loss in both engine speed and vehicle speed over that of shifting pattern 14. Under severe operating conditions, the vehicle may accordingly have insufficient momentum to justify a shift to the next higher gear, thereby defeating the purpose of engine speed limit 10. What is needed under such conditions, is the ability to increase engine speed up to rated engine speed 12 before shifting to the next higher gear as illustrated by shifting pattern 18 in FIG. 1, wherein engine speed following a shift should ideally remain above a peak torque engine RPM 15. This scenario would improve grade climbing performance as well as the likelihood of successfully completing the shift, wherein both of these improvements result from additional kinetic energy present in the vehicle prior to the shift and from the increased engine power and response after the shift. However, while sufficient engine speed for grade climbing and the like is necessary, there is also a need for limiting engine output conditions during such grade climbing or other operation so as to maintain fuel efficient engine operation.
What is therefore needed is a system for controlling drivetrain components, which may include an internal combustion engine and a change gear transmission, to thereby achieve desired fuel economy goals while also allowing for additional engine output only when the need therefore legitimately exists.
The foregoing shortcomings of the prior art are addressed by the present invention. In accordance with one aspect of the present invention, a system for controlling a vehicle drivetrain comprises a memory having stored therein an engine output characteristics map for an internal combustion engine and a number of fuel consumption contours associated with the map, and means for establishing a region of the engine output characteristics map wherein engine operation is undesirable, the region defining a first border as a function of at least one of the fuel consumption contours and a second border intersecting the first border.
In accordance with another aspect of the present invention, a method of controlling a vehicle drivetrain comprises the steps of establishing in memory an engine output characteristics map for an internal combustion engine, defining a number of fuel consumption contours associated with the engine output characteristics map, defining a first border relative to the engine output characteristics map as a function of at least one of the fuel consumption contours, and defining a second border relative to the engine output characteristics map and intersecting the first border, the first and second borders defining a region of the engine output characteristics map wherein engine operation is undesirable.
In accordance with yet another aspect of the present invention, a system for controlling a vehicle drivetrain comprises a memory having stored therein an engine output characteristics map, a region thereof of undesirable engine operation and a number of fuel consumption contours associated with the engine characteristics map, the region having a first border defined as a function of at least one of the number of fuel consumption contours and a second border intersecting the first border, and a control computer controlling engine operation according to the engine output characteristics map while maintaining or encouraging engine operation outside the region.
In accordance with still another aspect of the present invention, a method of controlling a vehicle drivetrain comprises the steps of providing an engine output characteristics map for an internal combustion engine, providing a number of fuel consumption contours associated with the map defining a region of the engine output characteristics map of undesirable engine operation, the region having a first border defined as a function of at least one of the fuel consumption contours and a second border intersecting the first border, and controlling engine operation according to the engine output characteristics map while maintaining or encouraging engine operation outside the region.
In accordance with a further aspect of the present invention, a system for controlling a vehicle drivetrain comprises a memory having stored therein an engine output characteristics map of an internal combustion engine and a contour associated with the map extending from a low engine load value to a high engine load value thereof, means for determining at least one engine operating parameter, and a control computer responsive to the at least one engine operating parameter to control shift points of a transmission coupled to the engine as the at least one engine operating parameter approaches the contour.
In accordance with yet a further aspect of the present invention, a method of controlling a vehicle drivetrain comprises the steps of providing an engine output characteristics map for an internal combustion engine, establishing a contour in relation to the map extending from a low engine load point to a high engine load point thereof, determining an engine operating parameter, controlling upshift points of a transmission coupled to the engine if the engine operating parameter approaches the contour from a first side thereof, and controlling downshift points of the transmission if the engine operating parameter approaches the contour from a second opposite side thereof.
In accordance with still a further aspect of the present invention, a system for controlling a vehicle drivetrain comprises a memory having stored therein an engine output characteristics map of an internal combustion engine and a contour associated with the map extending from a low engine load value to a high engine load value thereof, means for determining at least one engine operating parameter, and a control computer responsive to the at least one engine operating parameter to control an effective gear ratio of a continuous variable transmission (CVT) coupled to the engine to thereby maintain the at least one engine operating parameter within a predefined engine speed deviation from the contour.
In accordance with still another aspect of the present invention, a method of controlling a vehicle drivetrain comprises the steps of providing an engine output characteristics map for an internal combustion engine, establishing a contour in relation to the map extending from a low engine load point to a high engine load point thereof, determining an engine operating parameter, and controlling an effective gear ratio of a continuous variable transmission (CVT) coupled to the engine to thereby maintain the engine operating parameter within a predefined engine speed deviation from the contour.
In accordance with yet a further aspect of the present invention, a system for controlling a vehicle drivetrain comprises a memory having stored therein an engine output characteristics map and a region thereof of undesirable engine operation, a control computer operable to compute an estimated engine torque and an actual engine torque, the control computer allowing engine operation anywhere on or within the engine output characteristics map if the actual engine torque is greater than the estimated engine torque and otherwise maintaining or encouraging engine operation outside the region.
In accordance with still a further aspect of the present invention, a method of controlling a vehicle drivetrain comprises the steps of providing an engine output characteristics map for an internal combustion engine, defining a region of the engine output characteristics map of undesirable engine operation, determining an estimated engine torque value, determining an actual engine torque value, and controlling engine operation according to the engine output characteristics map while maintaining or encouraging engine operation outside the region if the actual engine torque is below the estimated engine torque.
In accordance with yet a further aspect of the present invention, a method of controlling a vehicle drivetrain comprises the steps of providing an engine output characteristics map for an internal combustion engine, determining at least one engine operating parameter in relation to the map, monitoring engine speed of the engine, if the engine speed is increasing along a boundary of the map, performing one of the following steps when the engine speed reaches a governed speed value: forcing an upshift to a higher gear of a transmission coupled to the engine, and limiting engine speed of the engine to the governed engine speed value.
In accordance with still a further aspect of the present invention, a method of controlling a vehicle drivetrain comprises the steps of providing an engine output characteristics map for an internal combustion engine, determining at least one engine operating parameter in relation to the map, monitoring engine speed of the engine, if the engine speed is decreasing along a boundary of the map, determining an engine speed shift point as a function of a gear step between a presently engaged gear and a next lower gear of a transmission coupled to the engine and performing one of the following steps when the engine speed reaches the engine speed shift point: forcing a downshift to the next lower gear of the transmission, and limiting engine speed of the engine to the engine speed shift point.
One object of the present invention is to provide a system for controlling engine operation to thereby maximize fuel economy, particularly during transmission gear shifting operations.
Another object of the present invention is to provide a system for controlling shift points of a number of gears of a transmission to thereby achieve fuel efficient engine operation.
Still another object of the present invention is to provide a system for controlling shift points of a number of gears of a transmission to thereby achieve high performance engine operation.
A further object of the present invention is to provide a system for controlling an effective gear ratio of a continuous variable transmission (CVT) to thereby achieve fuel efficient engine operation.
Yet another object of the present invention is to provide a system for controlling engine operation based on a comparison between an estimated engine torque and an actual engine torque to thereby achieve fuel efficient engine operation.
These and other objects of the present invention will become more apparent from the following description of the preferred embodiments.